The present invention relates to methods for water purification processing and the economic utilization of waste waters produced from water purification processing.
The disposal of saline water has become an expensive problem for society. For example, approximately 1.61 billion gallons of water containing approximately 800,000 tons of mixed sodium, calcium and magnesium chlorides and sulfates is produced from water treatment operations and oil fields in the state of California alone. This saline water must be disposed of, costing the state millions of dollars each year. Meanwhile, the United States Geological survey recently determined that New Mexico has an astounding 15 billion acre feet of brackish ground water, and a single basin in West Texas alone was found to have 760 million acre feet of brackish ground water.
Many coal beds are located where traditional mining is not feasible. Instead, the coal beds are stripped of their associated methane by pumping water from the coal bed strata. Methane migrates to gas wells where it is pumped out and transported for public use. The removed water is usually of moderate salinity, typically 900 to 1500 parts per million (ppm) of total dissolved salts (TDS). Unfortunately, the water is typically high in sodium and carbonate and/or bicarbonate.
Meanwhile, the disposal of waste water has become even more problematic in other parts of the world. As a result, billions of dollars are spent each year toward efforts to dispose of waste waters. Accordingly, it would be highly advantageous to provide improved methods of disposing of salty waters. It would even be more advantageous to provide methods of utilizing salty waters which provide a benefit to society, instead of simply disposing of the unwanted waters.
Water purification typically produces a first effluent of relatively “clean water” and a second effluent of “waste water” which includes unwanted contaminants. For purposes herein, clean water is defined to mean water including less than 0.05% by weight of the chloride, sulfate or carbonate salts of sodium, potassium, calcium or iron or combinations thereof. In addition to waste water, there is a substantial amount of “moderately saline water” around the world that has less salinity than waste water but which is not generally acceptable for irrigation or animal consumption. Thus, this moderately saline water has severely limited application and usefulness. As defined herein, “moderately saline water” means water that has 0.05% or more by weight and less than 1.00% by weight of the chloride, sulfate or carbonate salts of sodium, potassium, calcium or magnesium, or combinations thereof.
Known water purification processes proceed by numerous methods including ion-exchange, membrane softening, electrolysis, evaporation and precipitation. The softening of hard water take place by removing calcium and magnesium which is required for both industrial and household use. Known water softening processes proceed either by way of ion-exchange, membrane softening or precipitation. In the ion-exchange processes, the calcium (Ca2+) and magnesium (Mg2+) ions are exchanged for sodium (Na+) and the regeneration of the ion-exchange resin is achieved with a large excess of NaCl. This process creates a regeneration effluent being a relatively concentrated aqueous solution of sodium, calcium and magnesium chlorides which has to be discarded. Consequently, by this method, considerable amounts of sodium, calcium and magnesium salts in solution must be disposed of.
Alternatively, it is possible to soften water by using weak acid resins which exchange hydrogen (H+) for calcium (Ca2+) and magnesium (Mg2+), and to regenerate the spent resins with a mineral acid. While this method creates less waste water, it is more expensive and yields relatively acidic soft water which is corrosive. Meanwhile, membrane softening concentrates the calcium, magnesium salts and salts of other divalent ions to produce waste waters which require costly disposal.
The precipitation process has traditionally been carried out by the “lime soda” process in which lime is added to hard water to convert water soluble calcium bicarbonate into water insoluble calcium carbonate. This process also results in waste water which is difficult to filter and requires cumbersome treatment.
My previously issued patent, U.S. Pat. No. 5,300,123 relates to the purification of impure solid salts. Even this process produces salty waste water which must be disposed of. My later-issued patents U.S. Pat. Nos. 6,071,411 6,374,539 and 6,651,383 relate to the processing and utilization of processed waste waters. These processes preferably employ ion-exchange, preferably using sodium sulfate or calcium sulfate, to alter the salt content of treated water. Moreover, the resulting salts, clean effluents and waste water effluents are useful for various applications including the treatment of soils for improving dust control, soil stabilization, adjusting the soil's sodium adsorption ratio (SAR), and treating root rot.
Unfortunately, even with all of the various water treatment processes of the prior art, there are billions of gallons of waste water and moderately saline water that are discarded or not utilized because it is far too expensive to purify such waters using known water treatment processes. This overabundance of water is troubling because there is an overwhelming world-wide need for water, particularly for human and livestock consumption. A recent report from the United Nations states that more than 50 percent of the nations in the world will face water stress or water shortages by the year 2025. By 2050, as much as 75 percent of the worlds's population could face water scarcity.
Even more troubling, in impoverished countries humans and animals often suffer from calcium and magnesium deficiencies even though there may be millions of gallons of nearby saline waters. These saline waters typically contain some calcium and magnesium but are too high in sodium to be drinkable. Unfortunately, due to the expense and unavailability of equipment, this water cannot be processed for human or animal consumption.
Instead, milk is recommended to provide an adequate diet of calcium and magnesium but milk is typically not affordable or available in sufficient quantities to meet the needs of children in developing countries or even the needs of children in poor areas of developed countries. It would be an incredible development if the saline water could be treated to lower the sodium but increase or maintain the calcium and magnesium to levels suitable for human and livestock consumption.
Water is also in great demand for soil treatment, particularly for irrigation. Unfortunately, waste waters typically have saline content which is not suitable for nearby irrigation. Thus, it would be extraordinarily advantageous if an inexpensive process were developed for processing waste waters to produce an effluent suitable for irrigation.
Wind erosion of soil is also a significant problem throughout the world. Due to small particle size and poor cohesion, finely divided soil is sensitive to the influence of wind. Such finely divided soil is found in agricultural lands, dunes, lake beds, construction sites and roads under construction. Erosion by wind causes the drifting of masses of soil in the form of dust. The erosion by wind causes the inconvenience of dust formation and the loss of valuable matter such as seed, fertilizer and plantlets. Dust storms are a danger to traffic and a health risk to persons located in the vicinity.
Finally, it would be desirable if all of the aforementioned objectives could be accomplished while overcoming the expensive and problematic concerns facing this country and the rest of the world, specifically, the disposing of saline waters. It would further be desirable if this objective could be obtained while simultaneously meeting with above described needs.